Point taken CC, bad analogy on my part. I should have phrased that more in terms of how the toughest of armored objects has its vulnerabilities.
Some interesting research here.... apparently some M1's have fallen to more advanced weaponry... including some shaped charge rounds, not sabot...
Another Magic Bullet Theory
"According to an unclassified Army report, the mystery projectile punched through the vehicle’s skirt and drilled a pencil-sized hole through the hull. The hole was so small that “my little finger will not go into it,” the report’s author noted.
The “something” continued into the crew compartment, where it passed through the gunner’s seatback, grazed the kidney area of the gunner’s flak jacket and finally came to rest after boring a hole 1½ to 2 inches deep in the hull on the far side of the tank.
At this time, it appears most likely that an RPG-22 or some other improved variant of the Russian-designed weapon damaged the M1 tank, sources concluded. The damage certainly was caused by some sort of shaped-charge or hollow-charge warhead, and the cohesive nature of the destructive jet suggests a more effective weapon than a fragmented-jet RPG-7."